It's the debate that just keeps going round in, well, circles. Are Pirelli's tires good or bad for Formula One? Seven-time world champion Michael Schumacher has already said the tires are like "driving on raw eggs," while racing legend Jackie Stewart warns they are a danger.

Now double world champion Sebastian Vettel has weighed in.

The 24-year-old, who is leading the drivers' championship after four races, said racing was faster and more furious than ever -- largely thanks to the Italian tire manufacturer.

"The tires do see more degradation. It means we start to slide and then one guy slides more than the other because he puts his tires on two laps earlier," he said at a news conference ahead of this weekend's Spanish Grand Prix.

"It creates a different type of racing, more overtaking. Which I imagine is seen as better quality from the outside, simply because things happen. I think it depends what you really want."

The Red Bull driver said racing had undergone huge changes since refueling was banned in 2010. With cars now carrying more fuel, the toll on the tires has also greatly increased.

"It's so on a knife's edge with the tires that it's good and it's great for racing," he said. "It's great, it's mixed everything up, lots of overtaking, lots of things happening, fantastic for everybody."

Unsurprisingly the Italian company argues it should be congratulated. The manufacturer claimed it was simply responding to calls for more unpredictable racing, with director Paul Hembery saying: "We are pushing the limits."

When the Spanish Grand Prix takes place on Sunday, as many eyes will be on the tires as the drivers.

Vettel missed out on the quickest time in Friday practice by 0.164 seconds to Button. Rosberg was third ahead of Hamilton as McLaren, Red Bull and Mercedes look set to battle it out for the podium places again.

Fernando Alonso set Spanish hearts racing in the morning session by topping the time charts in his Ferrari, but was way down in 14th in the afternoon session, 1.201 seconds slower than Button.